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About the Authors:
Carlos David de Santana
* E-mail: [email protected]
Affiliations Division of Fishes, Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D. C., United States of America, Setor de Ictiologia, Museu Paraense Emilio Goeldi, Belém, Pará, Brazil
Richard P. Vari
Affiliation: Division of Fishes, Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D. C., United States of America
Wolmar B. Wosiacki
Affiliation: Setor de Ictiologia, Museu Paraense Emilio Goeldi, Belém, Pará, Brazil
Introduction
The order Gymnotiformes includes 33 genera and more than 200 extant species of Neotropical electric fishes plus one fossil form from the Late Miocene of Bolivia [1], [2]. Gymnotiforms inhabit freshwaters across the expanse from northern Argentina to southern Mexico in settings ranging from shallow, slow-flowing streams to deep rivers, with subsets of several families specialized for life in rapids and other high energy settings [3]–[6]. Species of gymnotiforms range in body size from miniatures of 50 mm total length such as Hypopygus minissimus [7] to the over 2.5 m total length of Electrophorus electricus [8]; a 50 times range notable in itself, but particularly striking in a lineage of circa only 200 species.
Arguably one of the most noteworthy characteristics of all gymnotiforms is their ability to produce electric organ discharges (EODs) which serve dual purposes - communication and exploration of the surrounding environment. Two alternative forms of such discharges occur among these electric fishes: pulse EODs (via myogenic organs) and wave EODs (via myogenic or neurogenic organs). Electrophorus is unique within the Gymnotiformes in having a third form of discharge of up to 600 volts used for hunting and self-defense [9], [10]. Such powerful discharges are dramatically apparent to anyone in contact with, or in close proximity, to these fishes in the water during a discharge. These shocks were reported by naturalists commencing early in the European exploration of the Neotropics, have been the subject of study by physiologists and are well known in popular lore [11].
Electrophorus was erected by Gill [12] to include the Electric Eel, Gymnotus electricus Linnaeus [13]. The description by Linneaus [13] was based on what was for the period a very detailed account and accompanying illustration by Gronovius [14] of a specimen probably originating in...